1. Field of the Invention
The present invention relates to miner cutting bit holders and, in particular, to miner bit holders which include a mounting base attached to a rotating cutting drum and a replaceable cutting bit holder.
2. Description of the Invention Background
In the materials mining industry it is typical to employ a mining apparatus which includes a vertically moveable rotating cutting drum which has cutting bits attached thereto. By virtue of the rotation of the cutting drum and the movement of the miner into the material to be mined, the material is removed for further processing.
It is well known that such cutting bits and their holders are subjected to considerable stresses during the mining operation. Such stresses occur axially, vertically and transverse relative to the cutting bit. Accordingly, in normal mining operations, cutting bits require frequent replacement due to wear or breakage. In fact, cutter bits must often be replaced on a daily basis. In view of this phenomenon, much effort has heretofore been directed to the provision of readily replaceable cutter bits which may be removed with a minimum of effort from their supports.
Because the bit holding devices are not the primary vehicles by which material is removed from the mine face, the bit holding devices are generally characterized by a longer service life. As such, the prior art has developed bit holding systems which include a bit holder which physically retains the cutting bit and which may be mounted in mounting base which may be directly or indirectly welded into the miner's cutting drum. Nevertheless, the bit holders themselves are subject to considerable wear and breakage and may require replacement on two to six month intervals.
It is also known that bit holders must be able to hold the cutting bits against axial movement while allowing the cutting bits to freely rotate in order to minimize wear in any single localized region. However, the cutting bit holder must be securely fastened to the mounting base because, if not, looseness will occur between the bit holder and the mounting base which will quickly accelerate into deterioration of either or both of those components.
While the prior art has endeavored to provide miner bit holders which include bit holders and separate mounting bases, Applicants have discovered that the prior art bit holding devices do not sufficiently restrain lateral, axial and vertical movement between a bit holder and a mounting base to eliminate movement therebetween and, thus, the associated problems resulting therefrom. As such, due to their design, prior art bit holder-mounting base combinations are prone to premature failure.
Accordingly, the need exists for a miner cutting bit holding apparatus which includes a bit holder which may appropriately restrain the cutting bit while being replaceably received within a mounting base attached to the cutting drum to eliminate relative movement therebetween and which, consequently, avoids failure of the bit holder and mounting base to eliminate the awaiting frequent replacement of one or both of those elements.